Build your dream bass amp!

Let's have some fun, and end up with a fine tube amp that you can't buy off the shelf.
Here's the scenario... I've got an old guitar amp chassis for a donor, an Acoustic model 164 100 watt tube amp. It has nice hefty output and power transformers, and is set up for 4 6L6 output tubes at around 100 watts output.
I'm going to gut it and build a bass head out of it, using turret board construction. Thinking of running 4 6550 tubes for the output section, but if I do I'd have to add a separate filament transformer. So let's think primarily 6L6 or EL34 output tubes.If you could marry the preamp from one amp and the output section from another, which would you choose? I'm thinking about an SVT preamp and a 100 watt Fender output stage. Not the ultralinear, the Bassman 100 that's like the old blackface Bassman upgraded to 100 watts output.I'm pretty old school and love the simple designs that rely on good design and bring out the best that a tube can deliver. Like the 5E3 Fender tweed clone I built a few years ago. Simple circuit with 2 volumes and one tone control...sounds like heaven into a Celestion Blue.
Soooo, what do you think? Help decide what to build and I'll post photos and updates as the project goes forward. I play a jazz bass in a blues band, and also do a lot of praise and worship work at church. I currently have an Acoustic 600b head and a couple of matching 4x10 cabs and want to make the jump to tubes. As a retired engineer and 40+ year guitar/bassist I love tube amps. All my guitar amps are tube, but I just began playing bass a few years back and this solid state Acoustic was my first bass rig. But I played a good tube head the other day and now I can't go back...so let's have some fun!

I'd love a rig where I could choose tones from a number of classic amps, run them into various speaker and mic combinations, save them all as presets, be able to EQ them all for the room then run them with lots of watts into a cab that can handle anything I throw at it.....oh, wait.....

Been thinking of doing something like this myself just to experiment with some spare iron and junkbox parts that i have lying around. To keep it simple but still somewhat flexible I would have 2 preamp channels, one with a standard Ampeg B15 James tonestack (do it with 12AX7's, 12AT7's or 6SL7's as you fancy) and do the other one with the Fender BMT tonestack (a'la Showman or Alembic F2B). Now you have an amp that could cop the B15 or Fender sound all in one. You could also couple the inputs together. Might get some interesting tonal possiblities.

I have always wanted a real two channel tube bass head. I'd think a Mesa style hot rodded Bassman channel plus a cleaner more smooth second channel akin to the Musicman heads. I would shoot for a Traynor YBA3 style output with EL34's at the high end of their output envelope.
I've also been jealous of gui****s with their silicon/tube rectifier choices, as well as triode/pentode outputs. It would be so nice to have tube rectified bass amps. I played a Standel or something once that was a 60 watt tube rectified bass amp. Sounded amazingly spongey.

I really like the two channels scheme on couple of my amps, just two jack inputs, each with their own gain and tone stack, in parallel with a overall volume control. Means you can run separate fx chains into the, and mute one etc. Overall I'm pretty much happy with this amp as it is, but KT88 power section would please me purely because I love the look of big bottles, but its not even lacking power with KT77.

You are asking a very complicated question. The first thing that you need to figure out is what features would best suit your needs. The thing is, what I like may not be what you are looking for.

How much control over the tone do you need? I understand your comment about the 5E3 into a Celestion Blue. I've built that same amp! Simplicity in the signal pathway is important for a pure tone. At the same time you say you are favoring an SVT pre which is quite far from that simple pathway.

I like the idea of adopting what works rather than trying to reinvent the wheel.

I'm biased but I like the B-15. Octal tubes 6SL7GT tubes in the preamp, James tone stack. An uncomplicated amp, pure tone, and one of the quietest amps you'll ever find. I often run mine flat, you could build the pre with a switch to take the tone stage in or out of the signal path. Part of what makes the B15 work is the higher power supply voltages. This allows them to bias the pre-amp tubes for optimal performance to get the sound they want. Look at Fender designs and you'll see lower voltages. They are different beasts.

The power supply needs to be designed with some ripple and sag in it. Too stiff and the amp is lifeless and looses touch sensitivity. I do favor a little more capacitance in the first power supply node than what is found in the typical Ampeg design. This helps with the low end and headroom. Finding just the right design parameters is what adds some of the magic to the way that the amp performs. I can't emphasize enough how important a good power supply design is.

The other important consideration is the transformers. For bass, I like heavy iron. The original Ampeg V4B is an amp that people loved. It had more iron than other amps in it's class. This came across as great tone. Don't skimp on the output transformer. I like the sound and performance of a V4B power amp.

Unless real estate on the chassis is an issue, there is nothing wrong with a separate filament transformer. It can make the amp quieter. I like the 6550A output tube for bass. If you want a 200W amp, this is a good way to go. If you want less power, go with a quad of 6L6GC or EL34's (more dirt at a lower volume if desired).

The final consideration is the speaker cabinet. The speakers interact with the amp to produce the final sound. The cabinet used shouldn't be an afterthought.